This project involves study of the anatomical properties and organization of cells in the visual system of primates, with emphasis on the retina and the visual cortex. The studies include (1) the anatomical association of outer-retinal cells selectively stained with tissue-reactive dyes and (2) the pattern distribution of cones in the retinas of human donors. Systematic study of the anatomical association at the light-microscope level of blue cones and horizontal and bipolar cells selectively stained by several tissue-reactive dyes in the macaque retina continues. The results have provided information on the probable retinal circuitry of the blue-sensitive cone pathway of primate retina. Retinal cone studies of eyes from human donors also continue. Evidence of a cone population with a point pattern resembling that of blue-sensitive cones selectively stained by tissue-reactive dyes has been obtained in quickly fixed, well-preserved retinas of some donors with a clinical history of diabetes. Cone density studies are being conducted on the retinas of macaques and human donors of various ages to resolve issues on the degree of primate photoreceptor losses with aging.